Telephonic receiver or transmitter



Dec) 15, 1925.

F. J. RElCHMANN TELEPHONIC RECEIVER 0R TRANSMITTER Filed June 25. 1923 Patented Dec. 15, 1925.

UNITED STATES PATENT OFFICE.

FRANK J". REICI-IMANN, 0F CHICAGO, ILLINOIS.

TELEPHONIC RECEIVER OR TRANSMITTER.

Application filed June 25, 1923.

T 0 all whom t may concer/z.:

Be it known that I, FRANK J. REICHMANN, a citizen of the United States, residing at `Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in a Telephonic Receiver or Transmitter; and I do hereby declare the following to be a full, clear, and exact description of thc invention, such as will en" able others skilled in the art to which it appertains to make and use the same.

My invention relates to telephonic apparatus for translating sound vibrations into current fluctuations, or for conversely translating fluctuations in an electric current into corresponding sound vibrations, and more particularly to means for increasing the efflcicncy of an apparatus of this kind. More particularly, my invention relates to an apparatus of this class in which a movable solenoid carrying the electric current is supported in a magnetic field and is mechanically connected to a diaphragm.

In constructing apparatus of this general class, it has heretofore been customary to support the solenoid by winding the same on a bobbin carried by one end of a lever which is pivoted intermediate of its ends and which has its other end connected to a sound reproducer, as shown for example in my copending application No. 574,299, filed July 11, 1922 on a loud speaking telephone receiver. Where such an apparatus is used in connection with a wireless receiving outt, it is highly important that the efiiciency of the effective energy transmission should be as high as possible and that the distortion of the transformed waves from electrical energy to mechanical vibrations or soundproducing energy be minimized. With this in mind, I am showing an arrangement in `my said companion application in which the solenoid is disposed within an annular air gap between two concentric magnet poles. By designing the various parts so as to minimize the width of this air gap, I have been able to produce a quite efficient apparatus, namely one which will effect loud and clear tone reproduction. However, I have found that both the efficiency of transformation and the exactness of reproduction of the original actuating sounds by means of which the current fiuctuations in the solenoid were initiated can be materially improved by employing the novel feature to which may invention relates, namely that of providing Serial No. 647,615.

means whereby the solenoid may be retained coaxial with the air gap during its vibratory movement without materially affecting the rigidity of its mechanical connection to the lever associated with the sound diaphragm.

That is to say, I have found that with aption provides simple, easily manufactured and inexpensive means for correcting these shortcomings, as will appear more fully from the following specification and from the accompanying drawings, from both of which further and more detailed objects of my invention will also appear.

Fig. 1 is a sectional view of a loud speaking telephone receiver embodying my invention.

Fig. 2 is an enlarged and fragmentary section through the solenoid and the adjacent magnet poles, taken when the lever arm by which the solenoid is supported extends at right angles to the axis of the annular magnetic field.

Fig. 3 is a fragmentary view on a smaller scale showing the position of the parts when the lever is tilted to an angle oblique to the said axis of the magnetic field.

Fig. 4 is a diagrammatic view, drawn with the proportions of some of the parts and the range of movement of the lever and solenoid exaggerated, showing one extreme position of the lever and solenoid as heretofore employed in similar constructions.

While my invention may readilybe employed in connection with movable solenoids as employed for a variety of purposes, it is particularly suited for use in connection with loud speaking telephone receivers. I am therefore illustrating it in such a connection, although I do not wish to be limited to any particular-use of my invention and particularly not since the same might be employed with equal facility in a telephone transmitter. l

Referring to the drawings, Fig. 1 shows a magnet of the inclosed type, in which a vertical core 1 of soft iron is connected by a circular iron base 2 and a substantially iron shell 3 to a perforated iron top plate 4 into the bore of which the upper end of the core 1 extends. The magnet as thus constructed is energized by a direct current flowing to a winding 5 which is interposed between the core 1 and the shell 3, thereby producing an annular magnetic field between the poles 1 and 4f of the magnet. Movably supported in this magnetic field is a solenoid 6 consisting of wire wound on an insulating spool or bobbin. This bobbin has its main cylindrical wall portion 6 integral with an upwardly tapering and frusto-conical extension7 leading to a horizontal and circular tip 8. rlhe said bobbin portions 6,7 and 8, together with a pair of outwardly directed flanges 9 at the upper and lower ends of the portion 6 are here shown as made integral with one another to form a cap and may desirably be molded from an insulating material such as bakelite. The tip 8 of this cap is centrally perforated to afford a bore for receiving a screw 10 by means of which the cap is tightly screwed to one end of the arm 11 of a lever which has the free end of its longer arm l2 fastened to the diaphragm 13 of a standard type of sound reproducer. rlhis lever is pivoted intermediate of its ends on a fulcrum 15 in the usual manner and. the sound reproducer is connected by an outlet tube 16 to an amplifying horn 17 of which only the adjacent neck portion is shown in the drawing.

lilith the apparatus thus arranged and with a fluctuating current flowing through the winding of the solenoid, the reaction of the magnetic field on these current fluctuations will cause the solenoid to vibrate axially in response to the periodicity of the fluctuations in the current, thereby producing corresponding vibrations of the diaphragm and hence causing the latter to emit the corresponding sounds. If the solenoid is continuously coaxial with the annular magnetic field, the effect of this field on all turns of the winding will be substantially the same, so that there will be no tendency to 'distort the waves which are being translated from an electrical form of energy into sound waves and no tendency towards movement of the solenoid other than axially of the magnetic field. However, if the solenoid is fastened to one arm of a pivoted lever, as in the case of Fig. 1, the movement of the solenoid is not in a straight line. Instead, it moves in an arc about thepivot 15 of the lever asa center and during the greater part of its travel its axis is tilted more or less at an angle to the axis of the magnetic field, as shown to an exaggerated degree in Fig. 4. As a result of this tilting of the solenoid with re spect to the magnetic field, the translated waves are somewhat distorted, thereby marring thel accurate reproduction of the sounds which are being transmitted. So also, part of the energy is wasted in friction in the apparatus, owing to the tendency of the magnetic field to swing the solenoid into true coaxial relation with this field. Consequently, the emitted lone reprorfluction is neither as clear nor as loud as it would be if there were no tilting of the solenoid with respect to the magnetic field.

According to one explanation which appears to be plausible, these undesirable effects may be due to the repelling action of a magnetic field on a wire which extends transversely of the flow of magnetic .lines in this field. This repelling thrust varies in direction with the direction in which current is flowing through the solenoid and varies in strength with the intensity of the magnetic field adjacent to the wire. For example, with the solenoid tilted as in Fig. 4 and with the current flowing in such a direction through the solenoid that the magnetic field will tend to push the wire away from the central or north pole of the magnet, the pushing action will be greater at the side A of the upper turn of the coil than at the side I3, and likewise will be greater at the side C of the lower turn than at the side D. Consequently, this thrust effect will tend to center the solenoid automatically and if the solenoid is tilted, it will tend to swing it out of its tilted disposition and into axial alinement with the magnetic field. Likewise, if the flow of current is reversed so that the pushing effect is away from the south pole of the magnet, the reverse difference in proportional effect will ensue, thereby also tending to untilt the solenoid coil. In either case, owing to this tendency, the energy due to the magnetic interaction will be spent partly in moving the solenoid along its own axis and partly in tending to straighten it, and this latter tendency asv transmitted through the lever will cause increased friction on the pivot of the lever', thereby reducing the efficiency of the apparatus.

Furthermore, with the solenoid coil thus tilted, the inequality of the magnetic effects in different portions of the solenoid may tend to distort the waves. At any rate, I have found that with a solenoid thus mounted for pivotal movement, both the efficiency of the 'energy transformation (or in the illustrated case, the loudness of the resulting tone reproduction) and the clarity of this tone reproduction can be improved by so constructing the parts that the solenoid will remain coaxial with the magnetic field in spite of' the pivotal movement of the lever. To accomplish this highly desir'- able effect, I arrange the support for the solenoid so that it will permit the above described thrust or pushing action of' the magnetic field to maintain the solenoid coaxial with that field without materially reducing the positive mechanical transmis sion of the endwise thrust on the solenoid to the lever which is connected to the soundreproducing diaphragm.

rIhis is readily accomplished after the manner sho/wn in Fig. 2 by making the tip 8 of the 'bobbin cap so thin that it can be flexed by a strain tending to rock the bobbin about the head of the screw 10, and by making the frusto-conical portion 7 also sufficiently thin so that it can yield slightly in response to the fiexing of the tip S, both of these parts being resilient so that they will automatically tend to regain their normal shapes when the strain ceases. Then the parts -of the bobbin cap are thus rthin and resilient, the tendency of the magnetic field to hold the solenoid coaxial with it when the lever is tilted to an angle oblique to the said axis, will permit the bobbin to adjust itself to such a position as that shown in Fig. 3, namely one in which its axis is tilted with respect to the axis of the screw l0. Owing to the tapering form of the portion 7 and to the relatively small required diameter of the tip 8, this thinning of the said parts does not interfere materially with the transmission of he mechanical thrust from the solenoid to the lever. In other words.l it merely provides the flexibility needed for permitting the axis of the bobbin and solenoid to tilt with respect to the axis of the screw, without creating a cushioning or yielding eHect such as would be produced by a diaphragm and such as would dampen the diaphragm and such as would dampen the resulting movement of the lever.

To control the extent of flexing of the tip 8 of the bobbin, I desirably interpose between it and the lever a washer 19 o-f smaller diameter than the said tip; as also shown in Figs. 2 and 3, so as to restrict the'flexing to the radially outer portion of the tip.v

By doing this I can secure the needed yielding in the connection between the bobbin and the lever without producing the undesirable sound effects which will occur if the flexibility is such as to permit the bobbin to swing this beyond the desired point and back again after the manner of a pendulum. In practice, I have found the desirable thickness of the bobbin tip and the desirable proportionate diameters of this tip and of the washer can readily be determined by experiments, and that a suitable proportioning ofthe parts, such as that illustrated in Fig. 2 results in a clearer tone production and in a greatly amplified volume. Moreover,

since my simple arrangement permits the` electromagnetic action to prevent the tilting of the bobbin with respect to the axis of the magnetic field, I can employ a smaller width of the magnetic gap with a bobbin which has its spool portion of a given thickness and hence can effect a further increase in the efficiency of the energy transformation.

However, `while I have illustrated and described my invention as applied to a particular type of telephonie apparatus and as accomplished in a. particular shape of solenoid bobbin, I do not wish to be limited to these or other details of the construction and arrangement thus disclosed, it being obvious that these might be varied in many ways without departing either from the spirit of my invention or from the appended claims. Neither do IA wish to be limited to its useY in connection with a lever connecting the solenoid to the diaphragm, as it might also be employed in connection with other supports for the solenoid. For example, I have found thatmy bobbin construction increases the loudness and clarity of a loud speaking telephone receiver even when the lever is omitted and the tip of the bobbin is connected directly to the dia.- phragin, this being perhaps due to diiiiculties of making the fastening exactly axial of both the bobbin and the diaphragm, and perhaps also to av lack of uniformity in the diaphragm which causes the latter to flex unsymmetrically.

Moreover, I have only given one explanation of the reasons for the superior results secured by my invention and do not wish to be limited by its degree of correctness or completeness.

I claim as my invention:

l. Means for connecting a solenoid-carrying spool to a rocking lever, comprising a cap having a hollow fru-sto conical side portion secured at its larger end to the spool and having a flat end connected to the smaller end of the said side portion, the entire. cap being formed of resilient material,V and means fastening the radially innerportion of the said tip to the lever while leaving the radially cuter portion of the tip free to be flexed.

2. Means for connecting asolenoid-carrying spool to a rocking lever, comprising a cap having a hollow frusto conical side portion secured at its larger end to the spool and having a flat end connected to the smaller end of the .sa-id side portion, the entire cap being formed of resilient material, a washer interposed between the lever and the tip of the cap and smaller in diameterl than the latter, and means extending through the washer for securing the radially inner portion of the said tip to the lever.

3. Means for connecting a solenoid winding to a rocking lever,"'comprising a spool carrying the solenoid, the spool having integral therewith a hollow cap comprising a frusto-conical portion tapering toward the lever and a flat tip closing the .smaller end of the said frusto-conical portion and disposed adjacent tro-the lever, fastening means extending thro-ugh the said tip axially thereof for Securing the cap to the lever, the entire cap being formed of a resilient material and the cap being sufficiently thin walled to permit a limited flexing thereof, and means interposed between the lever and the said tip for restricting the flexing of the tip to the radially outer portion thereof.

4L. Means for connecting a. solenoid-carrying spool toa rocking lever, consisting `of a conoidal cap made of resilient material and formed to permit a flexing of its tip more readily than a flexing of the cap portion connecting this tip fo the spool. means for fastening the central portion of the tip to the lever, and means associated with the. fastening means for restricting the flexing of the tip to the radially outer portion thereof.

5. Means for connecting a solenoid-carrying spool to a rocking lever, comprising a resilient conical cap connected at its larger end to the spool and having a flattened tip of relatively smaller size secured to the lever, and means for limiting the flexing of the tip to the radially outward portion thereof.

6. Means for connecting a solenoid-carrying spool to a support, comprising a resilient conoidal cap integral with the spooll and having its larger end connected to the spool, and fastening mea-ns disposed axially of both the spool and the cap for securing the said tip to the support, the tip being sufficiently flexible to permit a tilting of the spool With respect to it and the rest of the cap being sufficiently infiexible to maintain a rigid transmission of thrust-s between the spool and the support axially of the spool While permitting the said yielding of the tip.

7. Means for connecting a solenoid spool to a rocking lever, consisting of a hollow cap fastened at its mouth to the spool, and means extending through the center of the cap for securing the latter to the lever; the cap comprising a tubular portion formed to resist longitudinal strains, and a substantially flat and resilient tip disposed transverse of the axis of the cap; and means associated with the said tip for limiting the fiexing thereof to a radially outward portion of small Width relative to the radius of the tip. 8. In a telephonie receiver or transmitter, the combination with a diaphragm and a movable magnet spool, of a lever connected to the diaphragm, and a member constructed of resilient material and connecting the lever with the spool; the said member comprising a hollow frusto-conical portion fastened at its larger end to the spool substantially coaxial with the spool, and a substantially flat end portion secured at its center to the lever and at its periphery to the smaller end'of the aforesaid portion; the said flat portion being sufficiently thin to permit its being flexed by strains tending to tilt the axis of the spool with respect to the lever, the frustoconical portion being sufiiciently thin so that a distortion of the same Will permit the said flexing of the fiat end portion, and the frusto-conical formation of the first named portion affording rigidity in directions longitudinal of the spool to prevent a material change in the spacing between the spool and the connection of the flat end to the lever during the said fiexing and distortion.

Signed at Chicago, Illinois, June 21st,

FRANK J. REICHMANN. 

